Methods and apparatuses for polymer fibrillization under electric field

ABSTRACT

A method of fibrillizing a fibrillizable binder component of an electrode film can include providing a negatively charged fibrillizable binder component, and applying an electric field upon the negatively charged binder component to fibrillize the negatively charged fibrillizable binder component. A system for fibrillizing a binder component of an electrode film can include a mixing container made of a material having an affinity to donate electron(s) to the binder component, and an actuator configured to apply a force upon the mixing container so as to contact the mixing container with the binder component and to move the mixing container and the binder component relative to each other within a speed and range of motion sufficient to create an electrostatic force on the binder component and fibrillize the binder component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 14/642,471filed Mar. 9, 2015 and titled “METHODS AND APPARATUSES FOR POLYMERFIBRILLATION UNDER ELECTRIC FIELD”, which claims priority benefit toU.S. provisional Application No. 61/950,699, filed Mar. 10, 2014, eachof which is hereby incorporated by reference in its entirety for allpurposes.

BACKGROUND Field

The present invention relates to energy storage devices, particularly tomethods and apparatuses for fabricating dry particle films for use inenergy storage devices.

Description of the Related Art

There are many different types of energy storage devices used to powerelectronic devices, including for example capacitors, such as forexample, ultracapacitors or lithium-ion capacitors, batteries, such aslithium-ion batteries, and fuel cells. An energy storage device caninclude one or more films, such as an electrode film forming anelectrode of the energy storage device. The electrode film may compriseone or more active materials. The film can include a fibrillized bindercomponent, the fibrillized binder component providing a plurality offibrils which can support one or more other components of the film(e.g., providing mechanical structure for the film).

Fibrillization of binder components for electrode films can be typicallyperformed using a mechanical fibrillization process. Components of theelectrode film, including the binder component of the electrode film,can be combined and blended in an apparatus, such as, a blender, and/ora jet mill in which a strong shear force can be applied upon the bindercomponent to manipulate the binder component so as to form fibrils.Fibrillization of the binder component can facilitate formation of amatrix, lattice and/or web of fibrils in which one or more othercomponents of an electrode film, such as an active electrode material,can be supported. Fibrils of a binder component can provide desiredmechanical strength for an electrode film. For example, the fibrils canprovide films having desired resistance to a tensile, shear,compressive, and/or twisting stress, facilitating fabrication of energystorage devices having dry particle electrode films.

SUMMARY

One embodiment includes a method of fibrillizing a binder component ofan electrode film. This embodiment can include providing a negativelycharged fibrillizable binder component, and fibrillizing the negativelycharged fibrillizable binder component by applying an electric fieldupon the negatively charged fibrillizable binder component.

In some embodiments, applying the electric field can include applying anelectrostatic field.

In some embodiments, providing the negatively charged fibrillizablebinder component can include contacting a fibrillizable binder componentwith an electron donor.

In some embodiments, contacting the fibrillizable binder component withthe electron donor can include applying an acoustic force upon thefibrillizable binder component. The electron donor may include a mixingcontainer of a fibrillization apparatus, where the mixing container ismade of a material having an affinity to donate electrons to thefibrillizable binder component. In some embodiments, contacting thefibrillizable binder component with the electron donor can includeapplying at least one of a linear force and a rotational force upon themixing container to displace the mixing container relative to thefibrillizable binder component.

In some embodiments, providing the negatively charged fibrillizablebinder component can include contacting the fibrillizable bindercomponent with a mixing medium.

In some embodiments, the method can further include drying thefibrillizable binder component prior to applying the electric field uponthe negatively charged fibrillizable binder component. Drying thefibrillizable binder component can include heating the fibrillizablebinder component in a vacuum oven.

In some embodiments, the fibrillizable binder component can includepolytetrafluoroethylene.

Another embodiment includes a system for fibrillizing a binder componentof an electrode film. This embodiment can include a mixing containerincluding a material having an affinity to donate one or more electronsto the binder component, and an actuator configured to apply a forceupon the mixing container to contact the mixing container with thebinder component and to move the mixing container and the bindercomponent relative to each other within a speed and range of motionsufficient to create an electrostatic force on the binder component andfibrillize the binder component.

In some embodiments, the system can further include the binder componentand a mixing medium with a material having an affinity to transfernegative charge from the mixing container to the binder component. Themixing medium may include a same material as the binder component. Insome embodiments, the mixing medium and the binder component bothcomprise polytetrafluoroethylene.

In some embodiments, the actuator is further configured to apply a forceupon the mixing container to contact the mixing medium with at least oneof the mixing container and the binder component.

In some embodiments, the actuator is configured to apply an acousticforce to the binder component. In some embodiments, the actuator isconfigured to apply at least one of a linear force and a rotationalforce upon the mixing container.

In some embodiments, the mixing container can be made of an aluminummaterial. In some embodiments, the mixing medium may include a samematerial as the mixing container, such as the aluminum material.

In some embodiments, the system can further include a mixer forcombining the binder component with one or more other components of theelectrode film. The system may include a low shear mixer for combiningthe binder component with one or more other components of the electrodefilm mixture. In some embodiments, the system can further include anoven for drying the binder component and the one or more othercomponents of the electrode film.

Another embodiment includes a system which can have an electric-fieldgenerator, a container, and a fibrillizable binder component. Theelectric-field generator may be configured to apply an electric field tothe fibrillizable binder component and fibrillize the fibrillizablebinder component with the electric field when the fibrillizable bindercomponent is contained within the container.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages are described herein.Of course, it is to be understood that not necessarily all such objectsor advantages need to be achieved in accordance with any particularembodiment. Thus, for example, those skilled in the art will recognizethat the invention may be embodied or carried out in a manner that canachieve or optimize one advantage or a group of advantages withoutnecessarily achieving other objects or advantages.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription having reference to the attached figures, the invention notbeing limited to any particular disclosed embodiment(s).

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure are described with reference to the drawings of certainembodiments, which are intended to illustrate certain embodiments andnot to limit the invention.

FIG. 1 shows a cross-sectional view an example of an energy storagedevice including an electrode film on a surface of a current collector.

FIG. 2 shows a schematic view of an example of an apparatus forfibrillizing a binder component of an electrode film under an electricfield.

FIG. 3 shows a perspective view of another example of an apparatus forfibrillizing a binder component of an electrode film under an electricfield.

FIG. 4 shows an example of a process for fibrillizing a binder componentof an electrode film.

FIG. 5 shows an example of a process for fabricating an electrode filmincluding a fibrillized binder component.

FIG. 6A shows a scanning electron microscope (SEM) image, at 5 k×magnification, of an electrode film.

FIG. 6B shows a scanning electron microscope (SEM) image, at 1 k×magnification, of the electrode film shown in FIG. 6A.

FIG. 7A shows a scanning electron microscope (SEM) image, at 5 k×magnification, of an electrode film.

FIG. 7B shows a scanning electron microscope (SEM) image, at 1 k×magnification, of the electrode film shown in FIG. 7A

FIG. 8A shows a scanning electron microscope (SEM) image, at 5 k×magnification, of an electrode film.

FIG. 8B shows a scanning electron microscope (SEM) image, at 1 k×magnification, of the electrode film shown in FIG. 8A.

FIG. 9A shows a scanning electron microscope (SEM) image, at 5 k×magnification, of an electrode film.

FIG. 9B shows a scanning electron microscope (SEM) image, at 1 k×magnification, of the electrode film shown in FIG. 9A.

DETAILED DESCRIPTION

Although certain embodiments and examples are described below, those ofskill in the art will appreciate that the invention extends beyond thespecifically disclosed embodiments and/or uses and obvious modificationsand equivalents thereof. Thus, it is intended that the scope of theinvention herein disclosed should not be limited by any particularembodiments described below.

As described herein, mechanical processes of binder fibrillization caninclude application of high shear forces upon the binder. However,mechanical fibrillization processes in which high shear forces areapplied can result in damage of an active material component of theelectrode film mixture. For example, one or more surface properties ofan active material component, such as a carbon component of theelectrode film mixture, may be undesirably changed by the strong shearforce, diminishing a chemical and/or electrical property of the activematerial component. Mixing of electrode film components in a blenderunder high shear stress may also contribute to local heating of theelectrode film components in the blender. Such heating can furthercontribute to diminished chemical and/or electrical properties of one ormore active material components of the electrode film, and/or canprovide inefficient and/or non-uniform fibrillization of the bindercomponent.

One embodiment includes a method of fabricating an electrode film thatincludes fibrillization of a binder component using an electric field. Anegatively charged fibrillizable binder component can be subjected to anelectric field, such that the negatively charged binder component ismanipulated by the electric field to achieve fibrillization of thebinder component. In some embodiments, a negative charge can be placedupon a binder component to provide the negatively charged bindercomponent. For example, the binder component can be made from a materialhaving an affinity to receive one or more electrons (i.e., an electronacceptor) from a material having an affinity to donate one or moreelectrons to the binder component (i.e., an electron donor). Suitablebinder components may be made of a material having a high dielectricconstant, such as polyethylene (PE) and/or polytetrafluoroethylene(PTFE). Suitable material for an electron donor can include, forexample, aluminum. In some embodiments, the binder component can contactthe electron donor to transfer negative charge from the electron donorto the binder component.

In some embodiments, the electric field can be an electrostatic field.In some embodiments, an apparatus for fibrillizing a binder component ofan electrode film can be configured to generate an electrostatic field.In some embodiments, the fibrillization apparatus can be configured toplace one or more negative charges on the binder component such that thebinder component can be manipulated by the electrostatic field and thebinder component can be fibrillized. In some embodiments, thefibrillization apparatus can include a mixing container for providing anegative charge to the binder component. In some embodiments, thefibrillization apparatus can include a mixing medium to facilitatecharge transfer between the mixing container and the binder component.In some embodiments, the mixing medium can provide a negative charge tothe binder component. Contact between the mixing medium, the mixingcontainer, and/or the electrode film binder component can facilitatetransfer of electrons from the mixing container and/or the mixing mediumto the electrode binder component, and/or generation of theelectrostatic field. Movement of the mixing container, mixing mediumand/or the electrode film binder component relative to one another canfacilitate transfer of electrons and the generation of the electrostaticfield. Such contact and/or movement can be facilitated by applying forceto the mixing container, the mixing medium, and/or the electrode filmbinder component, including the electrode film mixture comprising theelectrode film binder component. For example, the apparatus forfibrillizing a binder component can be configured to generate anelectrostatic field and to expose a binder component comprisingpolytetrafluoroethylene (PTFE) to the electrostatic field such thatfibrillization of the PTFE binder component can be achieved.

In some embodiments, a fibrillization process using an electric fieldcan facilitate a process in which reduced shear stress is applied uponone or more components of an electrode film. Shear forces applied uponcomponents of an electrode film may be significantly diminished in anelectrostatic field fibrillization process. In some embodiments, anelectrostatic field fibrillization process can facilitate a process inwhich negligible shear stress is applied to components of an electrodefilm. In some embodiments, reducing shear stress can facilitate reduceddamage to one or more components of the electrode film, for examplerelative to a conventional shear-based fibrillization process. Forexample, electrochemical characteristics of an active material componentwithin the electrode mixture, such as activated carbon, can bemaintained when using an electrostatic field fibrillization process,relative to those characteristics prior to fibrillization of the bindercomponent within the mixture. In some embodiments, an electrostaticfibrillization process may facilitate effective fibrillization whilemaintaining physical and/or electrochemical integrity of active materialcomponents of the electrode film.

In some embodiments, energy storage devices, including ultracapacitors,batteries, and/or lithium based energy storage devices, such as forexample, lithium ion capacitors, and/or lithium ion batteries, can haveelectrode films made of a fibrillizable binder component that isfibrillized using an electrostatic fibrillization process. In someembodiments, maintaining one or more electrochemical characteristics ofan active material component within the electrode mixture may beparticularly advantageous for energy storage devices having electricalperformances which are more sensitive to the integrity of activematerial components. In some embodiments, maintaining one or moreelectrochemical characteristics of an active material component withinthe electrode mixture may be particularly advantageous for batteries,including lithium ion batteries.

In some embodiments, fibrillization of binder components using anelectric field can be advantageously integrated into one or more dryprocesses for fabricating electrode films. As used herein, dry processescan refer to one or more processes of electrode fabrication performed inthe absence or substantially in the absence of solvents, includingprocesses in which only or substantially only dry particles are used. Insome embodiments, fibrillization of binder components using electricfield can be integrated into a dry process for fabricating an electrodefilm to provide a free standing dry particles film.

In some embodiments, using an electric field, such as an electrostaticfield, to fibrillize a binder component of an electrode film canadvantageously facilitate a more efficient fibrillization process. Forexample, an electrostatic fibrillization process can provide anincreased number of fibrils from a quantity of binder material, anincreased uniformity in the fibrils formed, and/or improved mechanicalstrength of fibrils formed, relative to a conventional shear-basedfibrillization process.

In some embodiments, fibrillization using an electric field, such aselectrostatic fibrillization, can facilitate up to about a 5% reductionby weight of binder material used, including about a 2% reduction byweight of binder material used, relative to a conventional shear-basedfibrillization process. Reduced binder content and/or improvedelectrochemical integrity of an active material component may facilitateimproved electrical performance of the electrode film (e.g., improvingdevice equivalent series resistance, ESR, performance) relative to anelectrode film formed through a conventional shear-based fibrillizationprocess. In some embodiments, an ultracapacitor comprising electrodefilms fabricated using an electric field, such as electrostaticfibrillization, can demonstrate up to about 25% reduction in ESR ascompared to an ultracapacitor comprising electrode films fabricatedusing a conventional shear-based fibrillization process. In someembodiments, an energy storage device including one or more electrodefilms made of a binder component fibrillized using an electric field,such as an electrostatic fibrillization process can have at least abouta 10% to about 20% improvement in power and/or energy performancerelative to an energy storage device prepared under similar conditionsusing a conventional shear-based fibrillization process.

FIG. 1 shows an example of an energy storage device 100. The energystorage device 100 can include an ultracapacitor, and/or a battery. Theenergy storage device 100 can include a first electrode 102, a secondelectrode 104, and a separator 106 positioned between the firstelectrode 102 and second electrode 104. The separator can be configuredto electrically insulate two electrodes adjacent to opposing sides ofthe separator, such as the first electrode 102 and the second electrode104, while permitting ionic communication between the two adjacentelectrodes. The separator 106 can be made of a variety of porouselectrically insulating materials. In some embodiments, the separator106 can be made of a polymeric material. For example, the separator 106can be made of a cellulosic material (e.g., paper), and/or apolypropylene material.

In some embodiments, the first electrode 102 and/or the second electrode104 can include a first current collector 108, and a second currentcollector 110, respectively, for facilitating electrical couplingbetween the corresponding electrode and an external circuit. The firstcurrent collector 108 and/or the second current collector 110 can bemade of any combination of a number of suitable electrically conductivematerials. The first current collector 108 and/or the second currentcollector 110 can have various shapes and/or sizes suitable tofacilitate transfer of electrical charges between the correspondingelectrode and an external terminal, such as for example, a terminal ofan external electrical circuit. For example, a current collector caninclude a metallic material, such as an aluminum, nickel, copper, and/orsilver material. For example, the first current collector 108 and/or thesecond current collector 110 can include an aluminum foil having arectangular or substantially rectangular shape.

Referring to FIG. 1, the first electrode 102 and the second electrode104 can include electrode films 112, 114, and 116, 118 on a firstsurface and a second opposing surface of the electrode currentcollectors 108, 110, respectively. The electrode films 112, 114, 116and/or 118 can have a variety of suitable shapes, sizes, and/orthicknesses. For example, an electrode film can have a thickness ofabout 100 microns to about 250 microns.

In some embodiments, one or more of the electrode films 112, 114, 116and 118 can be made from an electrode film mixture comprising aplurality of dry particles. In some embodiments, one or more of theelectrode films 112, 114, 116 and 118 can be made from an electrode filmmixture comprising one or more carbon-based electroactive components(i.e., “active carbon”), including for example a porous carbon material,such as activated carbon (e.g., commercially available from KurarayChemical Co., LTD., of Osaka, Japan). In some embodiments, an electrodefilm mixture can include graphite, soft carbon, and/or hard carbon. Insome embodiments, an electrode film mixture can include one or moreadditives, including for example one or more additives for improvingelectrical conductivity of the electrode film (i.e., “conductivecarbon”). For example, an electrode film mixture can include aconductive carbon component, such as conductive carbon black (e.g.,Super P (ID commercially available from Timcal Graphite & Carbon, ofBodio, Switzerland).

The electrode film mixture can include one or more additives forenhancing the structural integrity of the electrode film, such as abinder component. In some embodiments, the binder components can includeone or more of a variety of polymers having an increased dielectricconstant. In some embodiments, polyethylene (PE) can be suitable,including ultra-high-molecular-weight polyethylene (UHMWPE). In someembodiments, polytetrafluoroethylene (PTFE) is suitable. Polymers ableto receive one or more electrons from an electron donor may be asuitable binder. The binder components can be fibrillizable binder. Forexample, one or more electrode films 112, 114, 116, 118 may include afibrillized binder component made of a fibrillizable binder componentwhich was fibrillized using an electric field, such as an electrostaticfibrillization process. As used herein, a fibrillized binder componentcan be structurally distinguished from a fibrillizable binder componentby a person having ordinary skill in the art using available scientificapparatus and methods, such as through observation of the size and/ornumber of fibrils.

Composition of the electrode films 112, 114, 116, and/or 118 may beselected to enable a desired electrode capacitance and/or resistanceperformance. In some embodiments, one or more of the electrode films112, 114, 116, and 118 can be made of about 50% to about 99% by weight(e.g., including about 85% to about 90% by weight) of activated carbon,up to about 20% by weight (e.g., including about 0.5% to about 15% byweight, including about 5% to about 10% by weight) of binder material,and up to about 25% (e.g., including about 1% to about 10%) by weight ofelectrical conductivity promoting material.

In one embodiment, an electrode film mixture can include about 70 gramsto about 100 grams (e.g., about 90 grams) of activated carbon, up toabout 5 grams of a conductive carbon additive component (e.g., about 2grams of a conductive carbon black material). The electrode film mixturecan include polytetrafluoroethylene (PTFE) as binder component. Forexample, the electrode film mixture can include about 5 weight % toabout 10 weight % of the binder component.

In some embodiments, one or more of the electrodes 102, 104 may befabricated using a dry electrode processing method. In dry processing,for example, an electrode film mixture comprising components of theelectrode film (e.g., electroactive material, electrical conductivitypromoting material and/or binder material) may be blended to form amixture. In some embodiments, the blended mixture is compressed to forma film-like structure, such as the electrode films 112, 114, 116 and118. In some embodiments, the electrode films 112, 114, 116, 118, can becalendared onto the corresponding current collector surface.

Forming one or more of the electrode films 112, 114, 116, and 118, canalso typically include fibrillization of the binder component. Forexample, fibrillization of the binder component can form fibrils, forexample, a web of fibrils, which can provide a matrix-like structure forsupporting one or more other components of the electrode film, such asactivated carbon and/or conductive carbon black.

In some embodiments, an electric field can be used to facilitatefibrillization of an electrode film binder component. As describedherein, a suitable binder component can include one or more polymershaving an affinity to receive one or more electrons from an electrondonor. For example, a suitable polymer for the binder component can havean increased dielectric constant, or a polymer able to readily acceptone or more electrons from an electron donor. The electric field can beused to apply a force upon the binder component carrying one or morenegative charges (e.g., a binder component which has received one ormore electrons from an electron donor), so as to facilitatefibrillization of the binder component.

As described further herein, the electrical, chemical, and/or mechanicalproperties of the active carbon and/or conductive carbon may beundesirably altered when subjected to a conventional high shear process,such as jet milling or blending, relative to the properties of thesematerials when subjected to the electric field processes describedherein. For example, when the active carbon and/or conductive carbon aremixed with a fibrillizable binder, and subjected to a high shearfibrillization process to fibrillize the binder, the active carbonand/or conductive carbon may be undesirable altered, resulting inreduced performance of the electrode film formed from these components.Such reduction in performance is reduced or eliminated when the sameelectrode components are combined, but the binder is fibrillized insteadthrough an electric field, such as through an electrostaticfibrillization process. Additionally, the fibrillizable binder may bemore efficiently fibrillized in an electric field, relative to aconventional high-shear process, resulting in a more efficient electrodewith reduced binder usage.

FIG. 2 is a schematic view of an example of an apparatus, such as anelectric-field generator 150 configured to apply an electric field, suchas an electrostatic field or other electric field, to a plurality ofcharged particles, such as fibrillizable binder particles 158. Theapparatus 150 may include a first charged portion 152 and a secondoppositely charged portion 154. For example, the first charged portion152 may have a positive charge and the second charged portion 154 mayhave a negative charge. As indicated by the arrow 156, an electric fieldextending from the positively charged portion 152 to the negativelycharged portion 154 can be provided, such as between the two chargedportions, 152, 154. The electric field provided by the positivelycharged portion 152 and the negatively charged portion 154 may exert anelectric force, such as an electrostatic force, upon charged particles158 exposed to the electric field. The chemical, electrical, and/ormechanical properties of the charged particles 158 may change whenexposed to the electric field. For example, the charged particles 158may be fibrillized by the force exerted upon the particles 158 by theelectric field provided between the first charged portion 152 and thesecond oppositely charged portion 154.

In some embodiments, the charged binder particles 158 may have anegative charge. As described herein, the binder particles 158 mayacquire a negative charge by accepting one or more electrons from anelectron donor. For example, the electric field generated by the chargedportions 152, 154 of apparatus 150 can exert a force upon the negativelycharged binder particles to fibrillize the binder particles. In someembodiments, as will be described in further details herein, a mixingcontainer may comprise the first charged portion 152, and a mixingmedium may comprise the second charged portion 154. For example, themixing container may donate one or more electrons to the mixing medium,the mixing container thereby acquiring a positive charge, and the mixingmedium acquiring a negative charge. An electric field, such as anelectrostatic field, may be generated by the positively charged mixingcontainer and the negatively charged mixing medium. Without beinglimited by any particular theory or mode of operation, force exertedupon one or more negatively charged binder particles by the generatedelectric field may change the properties thereof, for example, andthereby fibrillize, the binder particles. In some embodiments,negatively charged binder particles within the mixing container maycontribute to the electric field that exerts force upon charged binderparticles to fibrillize the binder particles.

FIG. 3 shows an example of a fibrillization apparatus 200 forfibrillizing an electrode film binder component. The fibrillizationapparatus 200 may include a mixing container 202 with an inner volumeconfigured to receive an electrode film mixture 206, including a bindercomponent. In some embodiments, the apparatus 200 can include a mixingmedium 204, to facilitate mixing of the electrode film mixture 206, andfibrillization of the binder component within mixture 206. For example,the mixing medium 204 and the electrode film mixture 206 may be mixedwhile received in the inner volume to achieve fibrillization of thebinder component within the mixture 206.

The inner volume of the mixing container 202 can have various suitableshapes and/or sizes suitable to contain the mixing medium 204 and/or theelectrode film mixture 206. In some embodiments, the inner volume of themixing container 202 can have a cylindrical or substantially cylindricalshape. In some embodiments, the inner volume of the mixing container 202can have a spherical or substantially spherical shape. In someembodiments, the inner volume of the mixing container 202 may comprise ashape configured to facilitate increased surface area contact forcontacting one or more components within the mixing container 202,and/or facilitate contact between these components and the container 202itself. For example, the inner volume of the mixing container 202 maycomprise a shape configured to provide desired surface area for contactbetween the mixing medium 204 and/or the electrode film mixture 206 andthe mixing container 202, and/or between the mixing medium 204 and theelectrode film mixture 206.

The size of the inner volume of the mixing container 202 can be selectedbased on various factors, including for example, a quantity of anelectrode film mixture for processing in the mixing container 202, amaterial of the mixing medium 204, and/or a composition of the electrodefilm binder component. In some embodiments, a size of the inner volumeof the mixing container 202 may be selected to provide sufficient spacewithin which the electrode film mixture 206 and/or mixing medium 204 canmove relative to the mixing container 202 and/or one another, when anamount of the electrode film mixture 206 and/or mixing medium 204 arecontained within container 202 for processing. For example, the innervolume of the mixing container 202 may include an amount of unoccupieddead space, when containing and mixing the electrode film mixture 206,and fibrillizing the binder component. For example, the mixing container202 can have an inner volume of sufficient size, relative to the volumeof the electrode film mixture 206 and mixing medium 204, to facilitatesufficient movement of the electrode film mixture 206 and/or mixingmedium 204 to provide desired contact between the mixing container 202and the mixing medium 204, between the electrode film mixture 206 andthe mixing medium 204, and/or between the electrode film mixture 206 andthe mixing container 202. Providing an inner volume within container 202with sufficient dead space, relative to the components contained withincontainer 202, such as the electrode film mixture 206 and mixing medium204, during processing, can facilitate fibrillization of the electrodefilm binder component. In some embodiments, the mixing container 202 hasa volume sufficient to facilitate generation of electrostatic field, soas to provide fibrillization of the electrode film binder component. Insome embodiments, the inner volume of the mixing container 202 may haveabout 5% to about 45% dead space, including about 5% to about 35% deadspace, with the remainder of the inner volume containing the electrodefilm mixture 206, or the mixing medium 204 and the electrode filmmixture 206. In some embodiments, the inner volume of the mixingcontainer 202 may have about 5% to about 20% dead space, including about5% to about 10% dead space, with the remainder of the inner volumecontaining the electrode film mixture 206, or the mixing medium 204 andthe electrode film mixture 206.

A mixing container 202 comprising too large of a dead space may reduceefficiency in generating the electrostatic field within the container202, reducing or preventing fibrillization of the binder component ofthe electrode film mixture 206. A mixing container 202 having too smallof a dead space may reduce or prevent desired movement of the mixingmedium 204 and/or electrode film mixture 206 within the container 202,reducing or preventing fibrillization of the binder component of theelectrode film mixture 206.

The mixing container 202 can be made of a material having an increasedaffinity to donate electrons, including natural and/or syntheticmaterials. For example, the mixing container 202 may comprise a materialwith an affinity to donate electrons to the mixing medium 204 and/or abinder component of the electrode film mixtures 206. In someembodiments, the mixing container 202 can be made of a materialcomprising a metal. In some embodiments, the mixing container 202 can bemade of aluminum, lead, and/or alloys thereof. In some embodiments, themixing container 202 can be made of a material comprising leather, fur,glass, polyamides (e.g., nylon), silk, cellulose (e.g., paper), and/orcombinations thereof. In some embodiments, at least a portion of themixing container 202 can be coated with one or more materials having anaffinity to donate electrons. For example, one or more surfaces of themixing container 202 can be coated with aluminum. In some embodiments,all or substantially all of the surfaces of a mixing container 202configured to be in contact with the mixing medium 204 and/or theelectrode film mixture 206, such as all or substantially all interiorsurfaces of the mixing container 202, are coated with aluminum. In someembodiments, one or more surfaces of the mixing container 202 can becoated with lead, including one or more surfaces configured to be incontact with the mixing medium 204 and/or the electrode film mixture206.

Material for the mixing medium 204 can be selected based on variousfactors, including for example, a material of the electrode film bindercomponent, and/or a material of the mixing container 202. In someembodiments, the mixing medium 204 can be made of a material having adesired tendency to accept one or more electrons from the mixingcontainer 202. For example, the mixing medium 204 can be an electronacceptor with respect to the mixing container 202, which can be theelectron donor. In some embodiments, the mixing medium 204 can have asufficient affinity to donate one or more electrons to the electrodefilm binder component. In this way, the mixing medium 204 can be theelectron donor with respect to the electrode film binder component. Insome embodiments, the mixing medium 204 can be made of material having asufficient tendency to accept one or more electrons from the mixingcontainer 202, while having a sufficient tendency to donate one or moreelectrons to the electrode film binder component. For example, themixing medium 204 can be configured to transfer one or more electronsfrom the mixing container 202 to the electrode film binder component. Insome embodiments, the mixing medium 204 may be made of material havingthe same or similar, or lower affinity, for donating a negative chargeas the mixing container 202 such that the mixing container 202 cantransfer negative charge to the mixing medium 204 with contact betweenthe mixing container 202 and the mixing medium 204. In some embodiments,the mixing medium 204 may comprise a material having the same orsimilar, or lower affinity for accepting a negative charge as the bindercomponent such that charge transfer from the mixing medium 204 to thebinder component may readily occur with contact between the two.

In some embodiments, the mixing medium 204 can be made of a naturaland/or synthetic material, including for example, wood, amber, rubber,silicon, and/or combinations thereof. In some embodiments, the mixingmedium 204 can be made of a metallic material, including aluminum,nickel, copper, brass, silver, gold, platinum, and/or combinationsthereof. In some embodiments, the mixing medium 204 can be made of apolymeric material, such as polyester, polyurethane (PU), polyethylene(PE), polypropylene (PP), polyvinyl chloride (PVC),polytetrafluoroethylene (PTFE, e.g., Teflon®) and/or combinationsthereof. In some embodiments, the mixing medium 204 can be selectedbased on an ease in maintaining desired chemical and/or physicalintegrity of the mixing medium 204. For example, the mixing medium 204can be selected based on an ease of cleaning and/or restoring one ormore properties of the mixing medium after its use. In some embodiments,the mixing medium 204 can be made of aluminum to provide transfer of anegative charge from the mixing container 202 to the binder component ofthe electrode film mixture 206. For example, the mixing medium 204 maycomprise a plurality of units made of aluminum.

The binder component comprises a fibrillizable binder, or may consistessentially of, or consist of a fibrillizable binder. For example, insome embodiments, the binder component comprises polytetrafluoroethylene(PTFE). In some embodiments, the mixing medium 204 comprises a materialhaving a desired tendency to donate electrons topolytetrafluoroethylene. In some embodiments, the mixing medium 204 maycomprise a material having a similar or same tendency to accept anegative charge as polytetrafluoroethylene. For example, the mixingmedium 204 may comprise polytetrafluoroethylene. In some embodiments,the mixing medium 204 may comprise a material having a lower tendency toaccept negative charge as polytetrafluoroethylene. In some embodiments,the binder component comprises polyethylene (PE), includingultra-high-molecular-weight polyethylene (UHMWPE). In some embodiments,the mixing medium 204 comprises a material having a tendency to donateelectrons to polyethylene and/or ultra-high-molecular-weightpolyethylene. For example, the mixing medium 204 may comprise a materialhaving about the same or lower tendency to accept a negative charge aspolyethylene.

The mixing medium 204 can include a plurality of units having varioussuitable sizes and/or shapes suitable to facilitate the electrostaticfibrillization described herein. In some embodiments, one or more unitsof the mixing medium 204 may comprise a shape configured to provide adesired surface area for contacting the mixing container 202 and/or theelectrode film mixture 206. In some embodiments, each unit of the mixingmedium 204 can have a spherical or substantially spherical shape. Forexample, the mixing medium 204 can comprise a plurality of metallicunits and/or polymeric units. In some embodiments, the mixing medium 204can include a plurality of polytetrafluoroethylene (e.g., Teflon®) unitshaving a spherical or substantially spherical shape. The units withinthe mixing medium can comprise various other three-dimensional shapes,such as rods, pins, cubes, pyramids, etc., and are not limited tospherical shapes.

A size of one or more units of the mixing medium 204 can be selectedbased on a number of factors. For example, the size of a unit of themixing medium 204 can be selected based on a balance of providingincreased surface area for contact with the mixing container 202 and/orthe electrode film binder component, and/or for carrying negative chargereceived from the mixing container 202, while providing units ofsufficient size to facilitate fibrillization of the binder component.For example, the units of the mixing medium can be sized with sufficientmass to facilitate mixing of the electrode film mixture. In someembodiments, the mixing medium 204 can comprise a plurality of sphericalor substantially spherical units having a diameter of about 1 millimeter(mm) to about 40 mm, including about 5 mm to about 15 mm. For example,each spherical or substantially spherical unit can have a diameter ofabout 12 mm. It will be understood that these dimensions can besimilarly applied to non-spherical embodiments. For example, the mixingmedium 204 can include units with non-spherical three-dimensional shapesthat have one or more dimensions (e.g., length, width, height, diameter)corresponding with the aforementioned diameters. For example, acylindrical rod with similar diameters can be employed.

The amount of mixing medium 204 to include in the fibrillizationapparatus 200, relative to other components, can be selected based uponvarious factors. For example, the amount of mixing medium 204 used canbe based upon the composition of the mixing medium 204 itself. Theamount of mixing medium 204 used can be based upon an amount and/or atype of the electrode film mixture processed by the fibrillizationapparatus 200. For example, the amount of mixing medium 204 can beselected to facilitate increased contact between the electrode filmbinder component, the mixing medium, and/or between the mixing container202. The amount of mixing medium 204 can be selected to facilitatetransfer of charge to the binder component, and/or generation of anelectrostatic field. The amount of mixing medium 204 can be selectedbased upon one or more of the above factors, while also reducing theamount of mixing medium 204 used. A reduced amount of mixing medium 204can increase the amount of electrode film mixture 206 that can beprocessed within the mixing container 202. In some embodiments, themixing medium 204 can be about 2 times to about 10 times the weight ofthe electrode film mixture 206, including about 3 times to about 8 timesthe weight of the electrode film mixture 206. For example, the mixingmedium 204 may be about 8 times the weight of the electrode film mixture206. In one embodiment, the mixing medium 204 can have a weight of about8 times that of the electrode film mixture 206 processed, including anelectrode film mixture comprising a polytetrafluoroethylene bindercomponent. Such ratios based upon weight between the mixing medium andthe electrode film mixture can provide improved surface contact andelectron donation between the components, while increasing the amount ofelectrode film mixture that is being processed.

As described above, contact between the mixing medium, the mixingcontainer, and/or the electrode film binder component can facilitatetransfer of electrons from the mixing container and/or the mixing mediumto the electrode binder component. Such contact between these componentscan facilitate generation of the electrostatic field for manipulatingthe negatively charged fibrillizable electrode film binder component.This electron transfer and electrostatic field generation can beprovided by moving the mixing container, mixing medium and/or theelectrode film binder component relative to one another, such as byapplying a force upon the mixing container, mixing medium and/or theelectrode film binder component.

The mixing container 202 can be moved in a variety of manners. Forexample, the mixing container can be moved manually or automatically.The fibrillization apparatus 200 can include one or more devices, suchas an actuator 201, shown schematically in FIG. 3, for applying alinear, and/or rotational force upon the mixing container 202. Suchforce(s) can translate to movement of container 202 in one or moredirections. The actuator 201 can include one or more motors, linearactuators, slides, bearings, or any of a number of suitable devicescapable of providing relative motion between container 202 and anothersupporting component, such as a base 203. In some embodiments, themixing container 202 can be moved in a lateral direction (e.g.,horizontally, as shown by the horizontal arrow 208, or into a horizontalplane of the view shown in FIG. 3). The mixing container 202 can bemoved in a vertical direction (e.g., vertically, as shown by verticalarrow 210 in FIG. 3). The mixing container 202 can be moved in an angleddirection (e.g., in a direction at an angle theta (0) greater than zero,and other than at a right angle relative to a horizontal plane, such asground, for example as shown by angled arrow 212 in FIG. 3). In someembodiments, the mixing container 202 can be rotated in a clockwisedirection (arrows 214), or in a counter-clockwise direction (arrows216). The container can be configured to move in any of a number ofdifferent lengths (arcs) and patterns, and can be moved throughvibration, oscillation, sonication, or through other methods, in one ormore of any of the aforementioned directions. In some embodiments, amagnitude of the force to the mixing container and/or a rate ofrepetition of the applied force can be selected to facilitate efficientfibrillization of the electrode film binder component of the electrodefilm mixture 206. For example, the magnitude of the force applied and/orthe rate of repetition of the applied force can be selected based on aweight and/or a material of the mixing container, mixing medium,electrode film mixture, and/or electrode film binder component. Examplesof suitable actuators 201 can include a paint shaker, an acoustic mixer,and/or the like. In some embodiments, the actuator 201 can include aresonant acoustic mixer.

In some embodiments, force can be applied to the mixing medium and/orelectrode film mixture to displace and move two or more of the mixingmedium, electrode film mixture (including its binder component) andmixing container relative to each other. For example, an actuator canuse sonication to agitate the mixing medium and/or the electrode filmmixture. A frequency of the sonication process can be selected based ona number of parameters, including for example, a weight and/or amaterial of the mixing container, mixing medium, electrode film mixture,and/or electrode film binder component.

In some embodiments, the fibrillization apparatus 200 can include one ormore components configured to prevent or substantially preventelectrical discharge by the mixing container 202, for example electricaldischarge to an electrical ground. In some embodiments, the mixingcontainer 202 can include an outer cover which is electricallyinsulating or substantially electrically insulating. For example, theouter cover can enclose or substantially enclose the mixing container202 so as to prevent discharge of electrical charge to ground by themixing container 202. In some embodiments, the mixing container 202 canbe positioned on an apparatus, such as a stand made of an electricallyinsulating or substantially electrically insulating material to preventor substantially prevent electrical discharge by the mixing container202. The mixing container cover and/or the apparatus upon which themixing container is positioned may be made of an electrically insulatingmaterial, and/or can be coated with an electrically insulating material.

FIG. 4 shows an example of a process 300 for fibrillizing an electrodefilm binder component using an electrostatic field, such as an electrodefilm suitable for use in an ultracapacitor and/or a battery. In block302, a mixing medium, such as mixing medium 204 as described withreference to FIG. 3, can be combined with components of the electrodefilm in a mixing container, such as mixing container 202 as describedwith reference to FIG. 3. The components of the electrode film caninclude a fibrillizable binder, which, when mixed with other electrodefilm components, such as activated and/or conductive carbon, form anelectrode film mixture. In block 304, a force can be applied to themixing container, the mixing medium, and/or the electrode filmcomponents. This force facilitates movement of the mixing container,mixing medium, and/or the electrode film binder component relative toone another, and/or facilitates contact between the electrode filmbinder component, mixing medium and/or the mixing container. Suchmovement and/or contact can result in fibrillization of the bindercomponent. For example, a force can be applied to the mixing container,such as by shaking the mixing container along one or more directions(e.g., horizontal, vertical, and/or at an angle other than horizontal orvertical), and/or by rotating the mixing container. For example, a forcecan be applied to the mixing components and/or mixing medium (e.g., anacoustic force).

FIG. 5 shows an example of a process 400 for fabricating an electrodefilm of an energy storage device. In block 402, components for anelectrode film can be combined. For example, components of the electrodefilm including the electrode film binder component, and othercomponents, such as an activated carbon component, and/or a conductivecarbon black component, can be combined. These components can be mixed,either during or after they are being combined, to form a homogenous orsubstantially homogenous electrode film mixture. In some embodiments,components of the electrode film mixture may be subjected to auniversalization process. For example, the universalization process mayuniformly or substantially uniformly mix the components of the electrodefilm mixture, such as creating a homogeneous or substantiallyhomogeneous mixture. Mixing and/or universalization of the components ofthe electrode film can be performed in a variety of suitable lower-shearmixing apparatuses, including for example a roll mixer and/or anacoustic mixer. In some embodiments, a lower-shear mixer may comprise aresonant acoustic mixer.

The mixing process can be performed for a period of time to achievedesired level of mixing of the electrode film components. In someembodiments, an electrode film mixture can be mixed in a roll mixer forabout 12 hours to about 20 hours to achieve a desired level of mixing.In block 404, the electrode film mixture can undergo a drying process.Drying of the electrode film mixture can be performed in an oven, suchas a vacuum oven. The drying process can aid removal of moisture fromone or more components of the electrode film to facilitate a moreefficient fibrillization process. For example, removal of residualmoisture from the electrode film mixture can facilitate transfer ofnegative charge from the mixing container and/or the mixing medium tothe electrode film binder component, and/or the generation of anelectrostatic field for manipulating negatively charged electrode filmbinder components. A temperature and/or duration of the drying processcan be selected, for example, based on a quantity of the mixture beingdried, and/or a degree of dryness desired (e.g., the amount of moistureremoval desired). In some embodiments, the drying process can beperformed at a temperature of about 70° C. to about 100° C., includingabout 80° C. to about 90° C. The drying process can be performed for aperiod of about 5 minutes to about 20 hours, including for example fromabout 5 hours to about 15 hours. For example, the drying process can beperformed at a temperature of about 85° C. for about 12 hours. In someembodiments, components of the electrode film may not undergo a dryingprocess.

In block 406, the electrode film mixture (e.g., mixture includingcomponents that underwent a drying process) can be combined in a mixingcontainer of a fibrillization apparatus (e.g., fibrillization apparatus200 of FIG. 3) with a mixing medium. In block 408, a force can beapplied to the mixing container, the mixing medium, and/or the electrodefilm mixture such that the mixing container, mixing medium, and/or theelectrode film mixture can move relative to one another, and/or tofacilitate contact between the electrode film binder component, mixingmedium and/or the mixing container. The force applied in block 408 canbe selected to facilitate increased contact between the mixingcontainer, the mixing medium, and/or the electrode film mixture,including the binder component. Without being limited by theory or anyparticular mode of operation, increased contact between the mixingcontainer, the mixing medium, and/or the electrode film bindercomponent, may facilitate increased transfer of electrons from themixing container and/or mixing medium to the binder component, and/orimprove generation of a desired electrostatic field for facilitatingfibrillization of the binder component. For example, increased contactbetween the mixing container, the mixing medium, and/or the electrodefilm binder component, may facilitate generation of a more uniformelectrostatic field, facilitating improved efficiency and/or uniformityin the binder fibrillization process. In some embodiments, the mixingcontainer can be shaken by applying a linear or substantially linearforce to move the mixing container back and forth along one or moredirection (e.g., a horizontal, vertical, and/or angled direction),and/or along an arced path around an axis (e.g., a horizontal, vertical,and/or angled axis). In some embodiments, a rotational force can beapplied to the mixing container. In some embodiments, a force can beapplied to the mixing medium and/or the electrode film mixture,including for example an acoustic force (e.g., a sonication process).

In block 410, the electrode film mixture can be calendared to form anelectrode film (e.g., one or more of electrode films 112, 114, 116, 118of FIG. 1). For example, the film mixture can be calendared to form afree-standing film. In some embodiments, the electrode film can beformed over one or more surfaces of an energy storage device currentcollector (e.g., one or more of current collectors 108, 110 of FIG. 1).In some embodiments, the electrode film can be calendared directly ontoa surface of a current collector. In some embodiments, an adhesivematerial can be used to facilitate adhesion of the electrode film to thesurface of the current collector.

Electrical performance of a first ultracapacitor, for example in a coincell configuration, fabricated using electrode films which underwentshear-based fibrillization was compared to the electrical performance ofa second ultracapacitor comprising electrode films fabricated using anelectric field fibrillization process. The electrodes of the twoultracapacitors included a binder component comprisingpolytetrafluoroethylene, activated carbon, and an electricallyconductive carbon black component. Fabrication of the twoultracapacitors included calendaring the fibrillized electrode filmmixtures onto respective current collectors. The electrodes of the twoultracapacitors were fabricated using dry particles electrode filmmixtures. The two electrodes of the two ultracapacitors were fabricatedusing mixtures comprising a fibrillizable binder component at about 8weight % to about 10 weight %, a carbon black component at about 0.5weight % to about 2 weight %, and an activated carbon component at about88 weight % to about 92 weight %.

The coin cell ultracapacitor comprising electrodes which underwentshear-based fibrillization demonstrated an equivalent series resistance(ESR) of about 1.22 Ohms (Ω) and a capacitance of about 0.606 Farads(F). The coin cell ultracapacitor comprising electrodes which underwentelectrostatic field fibrillization demonstrated an ESR of about 0.91Ωand a capacitance of about 0.588 F. As shown by the comparison, the coincell ultracapacitor comprising the electrodes fabricated usingelectrostatic field fibrillization demonstrated an ESR about 25% lowerthan that of the ultracapacitor comprising electrodes fabricated usingshear-based fibrillization, while maintaining comparable capacitanceperformance as that of the ultracapacitor comprising electrodesfabricated using shear-based fibrillization.

FIGS. 6A-9B show scanning electron microscope (SEM) images ofcross-section views of various electrode films made from variousrespective dry particles electrode film mixtures.

FIGS. 6A and 6B show two scanning electron microscope (SEM) images ofcross-section views of an electrode film 500. FIG. 6A shows across-section view of the electrode film 500 at 5 k× magnification andFIG. 6B shows a cross-section view of the electrode film 500 at 1 k×magnification. The electrode film 500 shown in FIGS. 6A and 6B wasfabricated without or substantially without a process in which theelectrode film mixture underwent repeated contact with a mixing mediumand/or a mixing container of a fibrillization apparatus (e.g., thefibrillization apparatus 200 as described with reference to FIG. 3). Theelectrode film 500 was formed using an electrode film mixture havingcomponents which were combined in a mixing apparatus (e.g., mixed in aroll mixer, for a period of at least about 12 hours) such that thecomponents of the electrode film 500 were uniformly or substantiallyuniformly mixed, and where the electrode film mixture was dried in avacuum oven (e.g., at about 85° C., for a period of about 12 hours) tofacilitate removal of any residual moisture. The electrode film 500included an activated carbon component, a conductive carbon blackcomponent and a binder component comprising polytetrafluoroethylene(PTFE). The dried electrode film mixture was subsequently calendared toform the electrode film 500, without or substantially without a processin which the electrode film mixture was shaken and/or otherwise agitatedwithin a fibrillization apparatus to provide repeated contact betweenthe electrode film binder component and the fibrillization apparatus.FIGS. 6A and 6B show that minimal, and/or no or substantially no fibrilswere formed in the electrode film. At higher magnification, FIG. 6Ashows a clearer view of PTFE particles 502 dispersed amongst theactivated carbon component 504 of the electrode film 500. As can be seenin FIG. 6A, the electrode film 500 included no or substantially no PTFEfibrils.

FIGS. 7A and 7B show two scanning electron microscope (SEM) images ofcross-section views of an electrode film 600. FIG. 7A shows across-section view of the electrode film 600 at 5 k× magnification andFIG. 7B shows a cross-section view of the electrode film 600 at 1 k×magnification. Components of the electrode film 600 were combined in amixing apparatus (e.g., a roll mixer, for a duration of at least about12 hours). The electrode film 600 included the same or substantially thesame composition as the electrode film 500 (e.g., including an activatedcarbon component, a conductive carbon black component and a bindercomponent comprising polytetrafluoroethylene (PTFE)). The electrode filmmixture was dried in a vacuum oven (e.g., at about 85° C., for a periodof about 12 hours) to facilitate removal of any residual moisture. Thedried electrode film mixture of electrode film 600 was combined in amixing container of a fibrillization apparatus (e.g., fibrillizationapparatus 200 of FIG. 3) with a mixing medium comprising PTFE beads(e.g., PTFE beads having a diameter of about 13 millimeters), where themixing container is made of a material comprising polystyrene. Theelectrode film mixture and the mixing medium were shaken in a mixingcontainer of the fibrillization apparatus for a period of about 15minutes, and the shaken mixture was then calendared to form theelectrode film 600. For example, the mixing container can be movedvertically (e.g., up-and-down), horizontally (e.g., left-and-right)and/or rotationally to facilitate fibrillization. FIGS. 7A and 7B showthat electrode film 600 includes minimal, and/or no or substantially nofibrils. For example, FIG. 7A shows PTFE particles 602 dispersed amongstactivated carbon component 604. Without being limited by any particulartheory or any particular mode of operation, a mixing container made of apolystyrene material may have insufficient affinity to donate negativecharge. For example, the polystyrene mixing container may haveinsufficient affinity to donate negative charge to the mixing mediumand/or binder component comprising PTFE, thereby preventing orsubstantially preventing generation of an electrostatic field in whichbinder components carrying negative charges may be manipulated to formfibrils.

FIGS. 8A and 8B show two scanning electron microscope (SEM) images ofcross-section views of an electrode film 700. FIG. 8A shows across-section view of the electrode film 700 at 5 k× magnification andFIG. 8B shows a cross-section view of the electrode 700 film at 1 k×magnification. Electrode film 700 had the same or substantially the samecomposition as electrode films 500, 600 of FIGS. 6A/6B and 7A/7B,respectively. For example, electrode film 700 included an activatedcarbon component, a conductive carbon black component and a bindercomponent comprising polytetrafluoroethylene (PTFE). The electrode film700 was fabricated using a process similar to that used to fabricateelectrode film 600, except that a mixing container made of an aluminummaterial was used in the fibrillization apparatus. Components of theelectrode film 700 were combined in a roll mixer, for a duration of atleast about 12 hours, and subsequently dried in a vacuum oven at about85° C., for a period of about 12 hours to facilitate removal of anyresidual moisture. The dried electrode film mixture of electrode film700 was combined in a mixing container of a fibrillization apparatussimilar to fibrillization apparatus 200 of FIG. 3 with a mixing medium.The mixing medium was made of substantially spherical PTFE units havinga diameter of about 13 millimeters. The mixing container was made of amaterial comprising aluminum. The electrode film mixture and the mixingmedium were shaken in the mixing container of the fibrillizationapparatus for a period of about 15 minutes. The shaken mixture was thencalendared to form the electrode film 700. Referring to FIGS. 8A and 8B,PTFE fibrils 702 can be clearly seen on surfaces of the activated carboncomponent of the electrode film 700, demonstrating effectivefibrillization of the binder component. Without being limited by anyparticular theory or any particular mode of operation, a mixingcontainer made of an aluminum material can have sufficient affinity todonate electrons to the mixing medium comprising PTFE beads and/or thePTFE binder component, facilitating placement of negative charges on thePTFE binder component and/or generation of an electrostatic field, suchthat the negatively charged PTFE binder component can be manipulated bythe electrostatic field, facilitating fibrillization of the PTFE bindercomponent.

FIGS. 9A and 9B show two scanning electron microscope (SEM) images ofcross-section views of an electrode film 800. FIG. 9A shows across-section view of the electrode film 800 at 5 k× magnification andFIG. 9B shows a cross-section view of the electrode film 800 at 1 k×magnification. The electrode film 800 had a composition similar to thatof electrode films 500, 600, and 700 described herein with reference toone or more of FIGS. 6A-8B. Components of the electrode film 800 weremixed, and the binder component was fibrillized using a high shearmechanical fibrillization process (by blending the electrode filmmixture in a jet mill). The electrode film mixture comprising themechanically fibrillized binder component was then calendared to formthe electrode film 800. FIGS. 9A and 9B show PTFE fibrils 802 onsurfaces of the activated carbon component 804 of the electrode film800. Based on comparison of FIGS. 8A, 8B with FIGS. 9A, 9B, it can beseen that fibrillization of a binder component using an electrostaticfield can provide results at least as comparable to that achieved by ahigh sheer mechanical fibrillization process, while achieving improvedelectrode performance, as described further above.

Although this invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that the invention extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses of theinvention and obvious modifications and equivalents thereof. Inaddition, while several variations of the embodiments of the inventionhave been shown and described in detail, other modifications, which arewithin the scope of this invention, will be readily apparent to those ofskill in the art based upon this disclosure. It is also contemplatedthat various combinations or sub-combinations of the specific featuresand aspects of the embodiments may be made and still fall within thescope of the invention. It should be understood that various featuresand aspects of the disclosed embodiments can be combined with, orsubstituted for, one another in order to form varying modes of theembodiments of the disclosed invention. Thus, it is intended that thescope of the invention herein disclosed should not be limited by theparticular embodiments described above.

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the devices and methodsdisclosed herein.

What is claimed is:
 1. A method of fibrillizing a binder component of anelectrode film, comprising: providing a negatively charged fibrillizablebinder component; and fibrillizing the negatively charged fibrillizablebinder component by applying an electric field upon the negativelycharged fibrillizable binder component.
 2. The method of claim 1,wherein applying the electric field comprises applying an electrostaticfield.
 3. The method of claim 2, wherein providing the negativelycharged fibrillizable binder component comprises contacting afibrillizable binder component with an electron donor.
 4. The method ofclaim 3, wherein contacting the fibrillizable binder component with theelectron donor comprises applying an acoustic force upon thefibrillizable binder component.
 5. The method of claim 3, wherein theelectron donor comprises a mixing container of a fibrillizationapparatus, wherein the mixing container is made of a material having anaffinity to donate electrons to the fibrillizable binder component. 6.The method of claim 5, wherein contacting the fibrillizable bindercomponent with the electron donor comprises applying at least one of alinear force and a rotational force upon the mixing container todisplace the mixing container relative to the fibrillizable bindercomponent.
 7. The method of claim 2, wherein providing the negativelycharged fibrillizable binder component comprises contacting thefibrillizable binder component with a mixing medium.
 8. The method ofclaim 2, further comprising drying the fibrillizable binder componentprior to applying the electric field upon the negatively chargedfibrillizable binder component.
 9. The method of claim 8, wherein dryingthe fibrillizable binder component comprises heating the fibrillizablebinder component in a vacuum oven.
 10. The method of claim 2, whereinthe fibrillizable binder component comprises polytetrafluoroethylene.